An Iranian Qadir light submarine and a hovercraft in Persian Gulf waters in late November, 2012.
Lenin Volga–Don Shipping Canal is a canal which connects the Volga River and the Don River at their closest points. Opened in 1952, the length of the waterway is 63 miles.I sometimes forget the scale of the map I see using Google Maps. The section of the Volga River below Volgograd looks like a thin little line when in fact it is a half mile wide channel.
The canal forms a part of the Unified Deep Water System of European Russia. Together with the lower Volga and the lower Don, the Volga–Don Canal provides the most direct navigable connection between the Caspian Sea and the Sea of Azov, and thus the world's oceans.
The actual construction of today's Volga–Don Canal began prior to WW2, which would interrupt the process. From 1948 to 1952, construction was completed; navigation was opened 1 June 1952. The canal and its facilities were predominantly built by prisoners detained in several specially organized corrective labor camps. In 1952 the number of convicts employed in construction topped 100,000.
As long as you are on good terms with Turkey and Russia, you can get big ships, including submarines, from the world's oceans into the Caspian Sea.
This is the same part of the world where Peter the Great was fighting the Turks.